Influence of different track structures on the development of corrugation in small radius curve section of subway

Many studies have shown that the rail corrugation on the small radius curve section of subway floating slab track is serious. And it seems to be different from the rail corrugation on the common track. The track structure must play an important role in the generation and development of rail corrugation. This paper measured a subway line in Tianjin, including 2 different track structures, and analyzed the measured data by using the international evaluation and acceptance indexes of rail corrugation. The results show that the inner rail of short sleeper monolithic track (SSMT) has poor smoothness in the wavelength range of 0-300 mm, and the overall smoothness of outer rail is good; the inner rail of steel spring floating slab track (SSFST) has poor smoothness in the wavelength range of 100-300 mm, and the outer rail has poor smoothness in the wavelength range of 300-1000 mm. Then the vehicle-track coupling model and wheel-rail wear calculation model is established. The calculation results show that in the existing rail corrugation, the short-wavelength rail corrugation of 20-25 mm will continue to appear or deteriorate, and the development of rail corrugation of other wavelengths will slow down or stop to varying degrees; with the increase of train passing times, the rail corrugation of SSFST with the wavelength of 315 mm develops the fastest, and the rail corrugation of SSMT with wavelengths of 20 mm and 160 mm develops the fastest

Influence of landform on the pressure distribution of explosion shock wave

The explosion site terrain and geomorphic environment will directly affect the shock wave pressure propagation and attenuation law and the shock wave test results uncertainty evaluation. In this study, the explosion site topographic and geomorphic parameters were analyzed, and the slope ratio and elevation difference within the region were proposed to parameterize the test site topographic and geomorphic characteristics. Using multi-physical field coupling simulation software, the finite element numerical simulation model of acoustic-solid structure coupling with different elevation difference and slope ratio is established and relevant research is carried out. The results show that when the pressure monitoring point is located at the test site low position, the elevation difference plays a role in attenuation of the shock wave pressure peak value, and vice versa; With the increase of the test site slope ratio, the shock wave pressure peak value at different test points gradually increases, and with the increase of the distance between the test points, the impact degree gradually decreases. Therefore, the elevation difference and slope ratio of the site shall be reduced as much as possible during the explosion shock wave pressure test, so as to improve the shock wave pressure test accuracy and the test data reliability, and provide theoretical support for the shock wave pressure test results uncertainty evaluation in the explosion field

An improved deconvolution beamforming algorithm for acoustic imaging of low signal-to-noise ratio sound sources in reverberant field

Most of the existing acoustic imaging studies in reverberant field ignore the influence of signal-to-noise ratio. As a result, commonly used beamforming algorithms in reverberant backgrounds have poor imaging accuracy for low signal-to-noise ratio sound sources. In response to that problem, an improved adaptive beamforming algorithm called SC-DAMAS is put forward in this paper. The algorithm replaces the free-field Green's function with the impulse response function, making the algorithm more suitable for acoustic imaging of low signal-to-noise ratio in a reverberant environment. Besides, the comparative simulation results with the conventional beamforming method and orthogonal matching pursuit algorithm-based DAMAS, as well as sound source acoustic imaging experiments are carried out to analyze its effectiveness. It is indicated that, in the reverberation field, the SC-DAMAS has no obvious sidelobes and achieves higher positioning accuracy for acoustic imaging of low signal-to-noise ratio sound source than the abovementioned counterparts, and its imaging test result is consistent with the actual situation, which verifies the effectiveness of the algorithm

Study of aircraft radial piston engines noise

The results of the study of acoustic characteristics of aircraft radial piston engines ASH-62IR and M-14P are presented. The tests were carried out during the race of the power plants of the AN-2 and Yak-18T light propeller-driven aircrafts under static conditions at the local aerodrome. It is shown that the method of organizing the exhaust of a multi-cylinder engine determines the main tone frequency. The influence of the engine power condition on the directivity of the tonal noise components is considered. The dependences of the sound power on the engine speed are obtained

Dynamic modeling and analysis of a vibration-driven robot driven by a conical dielectric elastomer actuator

This article aims to establish a theoretical model of a vibration-driven robot driven by a conical dielectric elastomer actuator and analyze its characteristics, in order to make up for the lack of theoretical model construction and parameter evolution analysis for this type of robot. This article introduces a vibration-driven robot driven by a conical dielectric elastomer actuator, and then establishes its dynamic model based on its electromechanical coupling and viscoelastic characteristics. Subsequently, simulation research is conducted using this model. Overall, this article derived a dynamic equation that can be applied to this type of robot, analyzed its motion characteristics, studied the effects of different parameters on it, and discussed the influence of viscoelasticity on vibration-driven robots. The proposed dynamic model and evolution law of vibration robots can provide theoretical guidance for subsequent control and optimization

Dynamic analysis of gear pairs with the effects of stick-slip

The instantaneous dynamic contact state analysis is carried out to reveal the process of scuffing failure of the gear tooth pair. A stick-slip dynamic model of a two-gear set is proposed and the coupling effects of time-varying mesh stiffness, tooth separations, friction between the gear teeth surfaces, and potential stick-slip are considered. Dynamic analysis shows that stick contact is an important source of tooth scuffing failure. Additionally, stick contact dramatically increases the vibration amplitudes and causes chaos. Parametric studies show that heavy load and rough tooth surfaces increase the probability of sticking and increase the time of stick state over a single mesh period. This study provides a design guard for avoiding scuffing failure and improving the reliability of gear transmission

On attractors in systems of ordinary differential equations arising in models of genetic networks

Two three-dimensional systems are considered, which have solutions with irregular behavior, tending to attractors. The comparison and comparative analysis are mad

Kinematic analysis and trajectory planning for a tree planting robot in forest environment

Tree Planting Machine (TPM) is subject to a Tree-Planting Robot (TPR) with desired tracking trajectory planning. In this topic, taking the TPR proposed as the analysis object, the positive and inverse solutions of the kinematics are analyzed to explore the optimal trajectory planning. An improved position/posture algorithm, based on the analytical solution of the inverse kinematics of the TPR, is proposed. The trajectory planning strategy for TPR in Cartesian coordinate system and Joint coordinate system is discussed, which is used for parabolic transition linear programming optimization, and the simulation model of TPR trajectory planning is constructed by MATLAB module. Numerical simulation results indicate that the deviation of the TPR trajectory from the expected value is significantly reduced. The proposed improved position/posture algorithm is verified by kinematic analysis, and the TPR followability and trajectory planning accuracy are greatly improved. Toward this goal, a variable trajectory planning can be effectively, and stability adjusted by pre-designed TPM system in the field of ecological tree planting

Analysis of ground motion measurement data under engineering blasting condition

To ensure that large precision instruments and equipment are in the best working condition, it is necessary to provide a suitable working environment for them. At this time, there is a high requirement for the vibration of the foundation at the location. Measuring the foundation vibration parameters, analyzing the foundation vibration state, and taking necessary damping measures during the construction process to provide basis are the premise of equipment installation and normal work. Combined with an application example, this paper briefly introduces the general situation of a project blasting, and obtains the basic characteristic parameters such as the peak velocity of ground motion and the time of arrival during the blasting operation; Based on the basic principle of regression analysis, the relationship between the peak velocity and the distance between the detonation centers and the charge weight is obtained by fitting the Sadovsky formula

Design and research of single leg walking mechanism of quadruped robot

A new single-degree-of-freedom quadruped robot leg walking mechanism is proposed to solve the problems of more drive elements, more complex structure and control system in existing single-leg walking mechanism. The principle scheme and structure design of the leg walking mechanism of the quadruped robot are completed according to the requirements of the foot end trajectory curve and the actual motion characteristics. The dimensions of each rod of the single-leg crank rocker mechanism to meet the “inverted D-type” motion law at the E point on the linkage are solved by using the Burmester four-rod mechanism integrated graphical method. The kinematic equations at the P point of the foot end of the proposed scheme are derived by using the kinematic analysis. By ADAMS simulation, the displacement and velocity curves at the P point of the foot end can well meet the requirements of the foot end movement law. The present methodology can not only achieve the goal of less driving elements and more simple design in single-leg walking mechanism, and can well meet the requirements of walking stability and smoothness of motion